In a vehicle having one or more prime movers, e.g., an internal combustion engine and/or one or more electric traction motors, torque is generated by the prime mover and delivered to a transmission input shaft. A transmission output shaft ultimately powers a set of drive wheels to thereby propel the vehicle. Within the transmission, a clutch may be controlled to selectively couple various rotatable members. When fully engaged, the clutch locks a pair of shafts together so that they may rotate in unison. The same clutch may also be allowed to slip so that the shafts rotate at different relative speeds.
Conventional hydraulic clutches are actuated using hydraulic pressure. Electromagnetic (EM) clutch assemblies may be actuated electrically, but may transmit torque mechanically. When an input voltage is applied to the EM clutch, a stationary magnetic field generates flux which passes into a rotor of the clutch assembly. The flux moves an armature into contact with the rotor. Slip occurs between the rotor and the armature until clutch lockup occurs. The armature separates from the rotor when the magnetic field is discontinued, thus disengaging the clutch assembly. Other EM clutch designs may exist that operate according to similar principals.